Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCB146

Poster Communications

The role of HDACs in the regulation of E3-ligases MuRF-1 and MAFbx expression in rat soleus at the early stage of muscle unloading.

T. Nemirovskaya1,2, E. Mochalova1,2, S. Belova1,2, B. Shenkman2

1. Faculty of Basic Medicine, Lomonosov Moscow State University, Moscow, Russian Federation. 2. Myology, IBMP, Moscow, Russian Federation.

Muscle unloading leads to its atrophy development. The MuRF-1 and MAFbx E3-ligases expression is increasing under this condition. Moresi et al. have shown that the histone deacetylases 4 and 5 signaling cascade (HDAC4/5) may regulate the expression of MuRF1 and MAFbx through the myogenin activation upon the muscle's denervation. We hypothesized that the HDAC 4 and 5 may regulate the E3 ligases expression in the early stages of muscle unloading, and the myogenin may be involved in this process. We checked this hypothesis by trichostatin A (inhibitor of HDAC4/5) administration in male Wistar rats (180-200 g) upon 3-day hindlimb suspension. Russian Bioethics Committee (protocol no. 418, 28.03.2017). The method of hindlimb suspension was described in Morey-Holton E & Globus R (2002). 24 animals were divided into 3 groups (n=8 in each): C-control, HST-hindlimb suspension with Trichostatin A (i.p. 0.6 mg/kg), or placebo (HS group) administration. The animals were anaesthetized with an i.p. injection of tribromoethanol (240 mg kg-1), soleus muscles were surgically excised, frozen in liquid nitrogen (Vilchinskaya NA et al., 2017). The Western blot and RT-PCR analyzes were done (three replicates of each sample). The Statistical analysis was performed using REST 2009 v.2.0.12 and Bio-Rad CFX Manager programs at the significance level set at 0.05. The significant differences between groups were statistically analyzed using Mann-Whitney test. All PCR data are expressed as median and interquartile range (0.25-0.75); all other data are given as mean ± standard error of the mean. HDAC4 protein content in soleus of HST group has decreased in nuclear fraction (in contrast to HS and C group by 88±6% and 86±7% respectively) and increased in cytoplasmic fraction in both suspended HST and HS groups by 33±10% and 21±9% respectively vs C group (p<0.05). On the contrary, the nuclear content of HDAC5 protein in the HST group didn't differ from those of C group, while this parameter in HS group was found to be significantly reduced by 41±10.2% (p <0.05). The Myogenin content in the HST group did not differ from that of the C group, while its amount in the HS group was significantly higher by 30±6% vs C (p <0.05). As for E3-lygases mRNA expression, MAFbx level in the HST group did not differ from those of control, while in the HS group it increased dramatically by 2.5 fold (1.75-3.5) (p <0.05). MuRF1 mRNA expression was equally elevated in both HS and HST suspended groups relative to the control (p<0.05). It could be concluded that The myogenin regulates the expression of MAFbx E3 ligase expression in the early stages of hindlimb unloading. The inhibition of HDAC 4 and 5 does not affect the regulation of MuRF1 E3 ligase expression. This work was supported by Russian Science Foundation (grant 18-15-00062).

Where applicable, experiments conform with Society ethical requirements